Compression behavior of historical brick masonry with mortar joint spalling strengthened with composite grouting and natural hemp fiber rope reinforcement

This study fabricated historical brick column specimens with mortar joint spalling. Modified composite sticky rice-lime mortar and natural hemp fiber rope were adopted and horizontal mortar joint grouting and fiber rope reinforcement were implemented to prepare performance-enhanced historical brick column specimens. The compression failure morphology and mechanical properties of the specimens with different strengthening conditions were studied, and the variation patterns of mechanical performance indicators with the strengthening conditions were analyzed. The calculation formula for the compressive strength was proposed, and the full stress-strain relationship model under compression and the crack length development model were established. The results show that the non-strengthened brick columns exhibit brittle failure morphology under compression, and the compressive strength and deformation modulus decrease with the increasing mortar joint spalling depth. The crack development process of reinforced brick columns under compression presents ductile characteristics. The compressive strength and crack density increase obviously and mortar joint grouting-fiber rope reinforcement significantly enhances the elastoplastic deformation capacity. The compressive strength, crack density, and elastic modulus of brick columns with the 12.5% grouting depth ratio and 0.125% reinforcement ratio increase by 57.4%, 7.9%, and 29.4%, respectively. The proposed strengthening method provides good engineering applicability.